VVER Emergency Cooling System Sump Protection Device, Filter Module of Sump Protection Device and Filter Element of Sump Protection Device

Abstract

Emergency Core Cooling System under loss-of-coolant accidents, including a sump protection device (SPD) in the emergency cooling system of a VVER, and the filter module and filter element of the sump protection device, which is to protect sumps from accumulation of debris in case of a loss-of-coolant accident.

Disclosed is a VVER emergency cooling system sump protection device, comprising a system of filters installed at the intake opening of the upper part of the sump located in the reactor containment bottom and connected to the intake of emergency cooling system pipeline. It consists of header-connected filter modules preventing debris from entering the intake of emergency cooling system pipelines; each filter module has slotted grates on sides and on top, and filter elements arranged inside are designed as laterally slotted filtration pipes and perforated distribution tubes (inside the pipes) the inner cavities of which are connected to headers.

Claims

1. A VVER emergency cooling system sump protection device characterized in that it comprises a system of filters installed at the intake opening of the upper part of the sump located in the reactor containment bottom and connected to the intake of emergency cooling system pipeline. It consists of header-connected filter modules preventing debris from entering the intake of emergency cooling system pipelines; each filter module has slotted grates on sides and on top, and filter elements arranged inside are designed as laterally slotted filtration pipes and perforated distribution tubes (inside the pipes), the internals of which are connected to headers.

2. A sump protection device as defined in claim 1, wherein the filter element pipes are perforated with helical slots.

3. A sump protection device as defined in claim 1, wherein the filter element pipes are made of wire with slots between turns.

4. A sump protection device as defined in claim 3, wherein the wire has a triangular profile.

5. A sump protection device as defined in claim 4, wherein the wire profile cross-section does not exceed 1.0×2.0 mm.

6. A sump protection device as defined in claim 1, wherein the slot size is does not exceed 1 mm.

7. A filter module for VVER emergency cooling system sump protection device as defined in claim 1 characterized in that it has slotted grates on sides and on top, and filter elements arranged inside designed as a set of laterally slotted filtration pipes and perforated distribution tubes (inside the pipes), the inner cavities of which are connected to headers.

8. A filter module as defined in claim 7, wherein the filter element pipes are perforated with helical slots.

9. A filter module as defined in claim 7, wherein the filter element pipes are made of wire with slots between turns.

10. A filter module as defined in claim 9, wherein the wire has a triangular profile.

11. A filter module as defined in claim 10, wherein the wire profile cross-section does not exceed 1.0×2.0 mm.

12. A filter module as defined in claim 7, wherein the slot size does not exceed 1 mm.

13. A filter element for the VVER emergency cooling system sump protection device as defined in claim 1, designed as a laterally slotted pipe with a perforated distribution tube (located inside the pipe). The diameter of holes in the tube gets successively reduced down the flow.

14. A filter element as defined in claim 13, wherein the diameter of holes in the perforated distribution tube at its end down the flow does not exceed half the diameter of holes at the beginning of the tube.

Description

[0037] As shown in the figures, at the bottom of the nuclear reactor containment (1) there are sumps (2), which are topped with filter modules (3) connected to the intake (6) of reactor emergency cooling system pipelines with the help of headers (4) via the intake (5) of the sump (2). The filter module (3) comprises a lateral slotted grate (7), top slotted grate (8) interconnected via top and bottom panels (9) and (10) (respectively) with the filter elements (11) fixed in between. The filter elements (11) are designed as filtration pipes (12) with distribution tubes (13) (located inside them) with holes (14) and (15) which get successively reduced in size down the flow.

[0038] The device operates in the following manner:

[0039] The reactor containment bottom (1) is of considerable size, which results in minimum coolant flow rate and creates a possibility for debris to settle along the coolant way to the sumps (2). The threshold velocity of debris that has reached the floor exceeds the settling velocity of debris in the flow. The filter modules (3) are placed at certain height from the bottom level. This provides for additional retention of debris that has reached the floor. Before entry into the sumps (2) and then into the intake (6) of the reactor emergency cooling system pipelines the coolant with debris passes through the filter modules (3) installed on top of the sumps (2) and connected with the sump (2) intake opening (5) by means of headers (4). Next, the coolant enters the filter module (3) through the lateral slotted grate (7) and top slotted grate (8). The outer surface of the slotted grates (7) and (8) has holes with clear dimensions of 17×170 mm, which provides entrapment of particles larger than 17 mm. The internal part of the slotted grates (7) and (8) forms inclined channels of rectangular shape and provides for deposition of particles with settling velocity over 0.017 m/s characteristic size of more than 200 μm for particles and fibers of class 4 and higher. The filter elements (11) are designed as filtration pipes (12) with openings. Openings of the filter elements (11) are rectangular helical slots, the length of which significantly exceeds their width. The slot width is 1 mm based on the minimum permissible particle size in the circulation system. The slotted shape of openings compared to the square one of the grid or perforated plate, reduces the risk of its clogging with particles smaller than the slot size when they simultaneously approach the slot. Via filtration pipes with holes (12), the flow enters distribution tubes (13) (inside the pipes) with openings (14) and (15), which get reduced in size down the flow. The surface area of the filter elements (11) is much larger than the area of the intake (6), which results in a substantially irregular flow of the coolant through the filter surface. To prevent this, distribution tubes (13) are installed inside the filter elements (11), they connect the internal cavity of the filter element (11) to the intake opening (6). The distribution tubes (13) have holes (14) and (15) of different diameters distributed throughout the length, which ensures uniform flow distribution over the filtering surface. The flow of coolant free from debris is discharged through the intake (6) to the pipeline of the reactor emergency cooling system.